Gound plane resistance calculator

[[email protected]]

[email protected] wrote:
Folks,

Is there an online tool, calculator or cheat sheet that lets me
calculate the resistance between two arbitrarily chosen points in a
ground plane?

All I found was heavily math-laden scholarly articles and instructions
how to program it in Excel. Reason behind this is that I am dealing with
a ground plane right now that can't be thicker than a few micrometers.

--
Regards, Joerg

http://www.analogconsultants.com/
This crops up in laser trim. One way to do the calculation is with
spice. You create a mesh of elements by using a program to generate
the spice netlist. Then you connect where appropriate.

You make the element with resistors set up as a square. That is, top,
right, bottom, left connected in series, with the edges being point in
the subcircuit. Then you build the array and tap.

For laser trim, it's a bit more complicated. Generally you connect
hard to the end of the array and then eliminate elements in the array
to do the trim.

In laser trim we never did that calc. We did meander cuts with empirical
determination of how fast and how far, or shadow cuts. After one
empirical hand-programming session we cut it loose and it produced
zillions of hybrids until someone yelled "enough".

Trimming thick film resistors, you cut across the resistor until you get
close, then cut along the length for fine trim... easily automated... did it
at Dickson Electronics, 1970-73.

There's many ways to do that. Meander cut, shadow cut, L-cut. We usually
didn't do L-cuts if avoidable because every second of laser time
counted. At tens of thousands of hybrids per year, 50+ resistors per,
and hard cost limits sometimes you have no choice. Luckily I always had
someone from the factory who knew how to minimize laser time. It's
almost like Fedex route planning.

Nowadays I guess direction change is easier but hardly anyone does
hybrids anymore. I can't even remember when I did the last one,
definitely 20+ years by now.

...Jim Thompson

[On the Road, in New York]

Still? What are you doing there? Trying to unseat the state governor?

Scooping up $$$$$ ;-)

Hope you like paying the NYS income tax! ;-)

 

[Joerg]

JetBlue is indeed classed as a low-cost or "no frills" carrier. As is
Southwest. A bit ironic these days, particularly for those travelling
in coach class.

It's all same class at Jetblue but the seats are very comfy. It's mostly
business people I saw on their flights.

As for no frills I am all for it. It really isn't such a big deal to
bring your own sandwich. Ok, once I overdid it and was kindly asked not
to do that again. Barbecued burgers the night before and packed two of
those right away, for a long trip to the east coast. When I opened the
aluminum foil a barbecue smell wafted through the cabin and had them all
drooling, including the Southwest flight attendants.

"If you travel as much as we do, you appreciate how much more
comfortable aircraft have become. Unless you travel in something
called economy class, which sounds ghastly."
-- Prince Philip

Yeah, right. He slurps Pommery up front in the big leather seats,
courtesy of the taxpayer. Do you guys still have to pay taxes to "the
crown"?

 

[Joerg]

Spehro Pefhany wrote: [snip]

JetBlue is indeed classed as a low-cost or "no frills" carrier. As is
Southwest. A bit ironic these days, particularly for those travelling
in coach class.

It's all same class at Jetblue but the seats are very comfy. It's mostly
business people I saw on their flights.

As for no frills I am all for it. It really isn't such a big deal to
bring your own sandwich. Ok, once I overdid it and was kindly asked not
to do that again. Barbecued burgers the night before and packed two of
those right away, for a long trip to the east coast. When I opened the
aluminum foil a barbecue smell wafted through the cabin and had them all
drooling, including the Southwest flight attendants.

[snip]

Can you really do that anymore? How do you get past TSA? I used to go on a
day trip to San Jose and bring back _pounds_ of pastrami and several bottles
of wine from a Los Altos deli... smelling to high heaven ;-)

Old (or new?) drill: I take 1-2 empty water bottles through TSA, then
fill at a fountain on the way to the gate. Sandwiches, burgers and other
goodies are in aluminum foil and/or ziplock, then in a small plastic
bag. This gets placed opened on one of those trays. One flight last year
was hilarious. Big dude from TSA picked it up and I thought "oh-oh". He
walked up to the rather lengthy line in front of the checkpoint, held up
the bag as high as he could and hollered with a drill sergeant's voice
"Listen up, folks, _THIS_ is how it's done correctly".

 

[Spehro Pefhany]

It's all same class at Jetblue but the seats are very comfy. It's mostly
business people I saw on their flights.

As for no frills I am all for it. It really isn't such a big deal to
bring your own sandwich. Ok, once I overdid it and was kindly asked not
to do that again. Barbecued burgers the night before and packed two of
those right away, for a long trip to the east coast. When I opened the
aluminum foil a barbecue smell wafted through the cabin and had them all
drooling, including the Southwest flight attendants.

One no-frills airline I took recently (Malaysia-based Air Asia) has a
rule prohibiting all outside food and beverages. Conveniently, they
sell food on board (actually not too bad stuff at quite reasonable
prices). Since Chinese tend to travel with enough food for an army
(some ancient racial memory of famine, no doubt) I don't think they
can really enforce it, but I imagine a rack of pork ribs might not be
appreciated.

Yeah, right. He slurps Pommery up front in the big leather seats,
courtesy of the taxpayer.

What really costs the big $$ are military flights for leaders.
Commercial flights in any class are practically free by comparison (at
least for the main figures).

Do you guys still have to pay taxes to "the
crown"?

Ah, essentially nothing- about $1.50 a year per citizen, which
includes the Governor General (0.003% of the economy). The current GG
took a 90% pay cut to serve (he was president of the University of
Waterloo). The Queen is sort of a time-share deal, when she's doing
something for us, the costs of that are supposed to be covered. There
are also benefits to being a member in good standing of the
Commonwealth of Nations. A very good deal, if you ask me.


Best regards,
Spehro Pefhany

 

[Joerg]

One no-frills airline I took recently (Malaysia-based Air Asia) has a
rule prohibiting all outside food and beverages. Conveniently, they
sell food on board (actually not too bad stuff at quite reasonable
prices). Since Chinese tend to travel with enough food for an army
(some ancient racial memory of famine, no doubt) I don't think they
can really enforce it, but I imagine a rack of pork ribs might not be
appreciated.

We just placed two small loaves of bread into the Weber. I guess those
wouldn't be appreciated either because they spread a meaty smell
throughout the room, depending on what else cooks in there.

What really costs the big $$ are military flights for leaders.
Commercial flights in any class are practically free by comparison (at
least for the main figures).

Well, except that this whole royal business is something that lots of
other countries perfectly do without. Meaning less military flights. But
if the population likes it, why not.

Ah, essentially nothing- about $1.50 a year per citizen, which
includes the Governor General (0.003% of the economy). The current GG
took a 90% pay cut to serve (he was president of the University of
Waterloo). The Queen is sort of a time-share deal, when she's doing
something for us, the costs of that are supposed to be covered. There
are also benefits to being a member in good standing of the
Commonwealth of Nations. A very good deal, if you ask me.

$1.50 is ok. But what are those benefits? The prime days of the big
Commonwealth are gone, I thought.

 

[Spehro Pefhany]

We just placed two small loaves of bread into the Weber. I guess those
wouldn't be appreciated either because they spread a meaty smell
throughout the room, depending on what else cooks in there.

I'd avoid pork on a Malaysian flight because the seat mates are likely
to be Muslim.

Well, except that this whole royal business is something that lots of
other countries perfectly do without. Meaning less military flights. But
if the population likes it, why not.

<shrug> A lot of the things they do are just done by other people. So
long as they don't have real power, it's not a big deal. The US
president has powers more like a king than anyone in a parliamentary
democracy, probably because that was the state of the art hundreds of
years ago.

$1.50 is ok. But what are those benefits? The prime days of the big
Commonwealth are gone, I thought.

There are a number of benefits to being 'less foreign' than others to
a group of 2bn+ people, especially for a middle power. One example is
the right to vote in elections (and even run for office) in a number
of other member countries (including the UK) if resident.

http://en.wikipedia.org/wiki/Commonwealth_of_Nations



Best regards,
Spehro Pefhany

 

[Joerg]

I'd avoid pork on a Malaysian flight because the seat mates are likely
to be Muslim.


<shrug> A lot of the things they do are just done by other people. So
long as they don't have real power, it's not a big deal. The US
president has powers more like a king than anyone in a parliamentary
democracy, probably because that was the state of the art hundreds of
years ago.


There are a number of benefits to being 'less foreign' than others to
a group of 2bn+ people, especially for a middle power. One example is
the right to vote in elections (and even run for office) in a number
of other member countries (including the UK) if resident.

I never had ambitions to become the mayor of Manchester

When I lived in the Netherlands as a foreigner I received a notice one
day that I was eligible to vote in the local elections. I thought that
was kind of nice but never got to exercise that new right on account of
getting my degree and moving away.

http://en.wikipedia.org/wiki/Commonwealth_of_Nations

Quote "The status of "Member in Arrears" is used to denote those that
are in arrears in paying subscription dues to the Commonwealth"

Hmm ... I guess they get more than that $1.50? That's why we kicked them
out a long time ago, because they wanted a whole lot more

 

[Spehro Pefhany]

She was expecting Eurosheep?

She had never seen livestock transported on an airline before. IIRC,
destination was a Slovakia derivative.

...Jim Thompson

[On the Road, in New York]

There's nothing worse than a flight with a bunch of old goats.


Best regards,
Spehro Pefhany

 

[Joerg]

Yes there is an extremely simple tool. I'm sending you a copy of
results on a3 by 5 inch PCB containing a microcontroller and 24 bit
data acquisition. I wanted the GND noise to be less than 1/4 LSB so
this tool QUANTIFIED the effects of parts palacement *and* cuts, even
includes via holes if you want. But it was nice to finally be able to
quantify 'improving' a PCB layout.

Thank you, Robert. Got your files, and the plot look very nice. This
time we just winged it but out of curiosity, what is that software? Did
you write it yourself?